The present invention relates generally to combine harvesters and, more particularly, to an adjustment mechanism for the sieves in a combine grain cleaning mechanism.
The cleaning mechanism in a combine harvester typically includes an upper chaffer sieve and a lower cleaning sieve. Grain received from the threshing and separating mechanism passes over the upper chaffer sieve where air is blown upwardly therethrough to remove chaff and other residual debris from the grain thereon to permit the grain to pass therethrough to the cleaning sieve where the cleaning action is duplicated. Each sieve is generally constructed of a series of transversely extending and pivotally mounted slats, each of which has a convoluted shape to define openings therethrough. The size of these openings, through which cleaned grain will pass, is determined by the pivoted position of the individual slats. Typically, a manual adjustment mechanism will interconnect all of the pivoted slats to control the pivoted position thereof and, therefore, the size of the openings through the sieve.
Generally, these adjustment mechanisms incorporate a handle mounted beneath the sieves to eliminate any problem of the handle impeding the flow of material over top of the sieve. However, accessing the adjustment handles on such cleaning sieves is often difficult because of raking members or other optional equipment mounted at the rear of the sieve, where access to the adjustment mechanism can be reached. Accordingly, it would be advantageous to provide a sieve adjustment mechanism in which the handle is mounted above the surface of the sieve in such a manner as not to affect the function of the sieve or obstruct the flow of crop material across the upper surface of the sieve.